Arthrobacter species as a prey cell reservoir for nonobligate bacterial predators in soil

Abstract

The possibility was investigated that, in soil, Arthrobacter species might serve as a major reservoir of prey cells for the nonobligate bacterial predators in the soil. Previous evidence had indicated this. Arthrobacter globiformis cells added to soil caused an increase in the total bacterial count and the gram-negative bacteria count of the soil. Copper-resistant bacterial predators, such as Cupriavidus necator, also increased in number, apparently in response to the A. globiformis cells. Other bacterial predators did not respond to A. globiformis. Certain soil bacteria responded specifically and quickly (within 2.5 h) to the A. globiformis cell additions. They had gliding motility and could hydrolyze GELRITE (the solidifying agent for media). Addition of these hydrolyzer bacteria to soil caused marked increases in the total bacteria count, the gram-negative bacteria count, and the bacterial predator counts. These responses mimicked those for A. globiformis soil additions. The results from an alternative method of soil incubation that speeded up the processes, and from other observations, indicated that the large apparent bacterial predator attack on A. globiformis in soil may actually be on other bacteria in soil that respond to A. globiformis in a nonpredatory manner. Therefore, A. globiformis and other Arthrobacter species may not be serving as a major reservoir of prey cells in soil.Key words: predation, predators, prey, soil, Arthrobacter.